An operation called a "posted read" can be performed on some digital busses. A posted read is a split bus transaction in the sense that a first device requests data from a second device on the bus in the first part of the transaction (i.e., it "posts" the read). Rather than occupying the bus while the second device retrieves the data and puts the requested data onto the bus, the first device releases the bus. When the second device is ready with the data, the second device obtains control of the bus and supplies the data onto the bus and to the first device in the second part of the transaction.
FIG. 1 illustrates one possible multimedia system involving a processor 1, a memory 2, a bus 3, a DMA (direct memory access) controller 4, a video encoder 5, a video display 6, an audio encoder 7, and a speaker 8. It may be desired to send video data stored in memory 2 to video display 6 and to send audio data stored in memory 2 to speaker 8. A DMA controller is sought which will supply the correct data to the video encoder and the correct data to the audio encoder when posted read operations are used on bus 3 to read the data from memory 2.